CN1207621A - Modulator - Google Patents
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- CN1207621A CN1207621A CN98116396A CN98116396A CN1207621A CN 1207621 A CN1207621 A CN 1207621A CN 98116396 A CN98116396 A CN 98116396A CN 98116396 A CN98116396 A CN 98116396A CN 1207621 A CN1207621 A CN 1207621A
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- frequency
- filter
- band
- trigonometric function
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
Abstract
A low frequency signal generating portion 1 generates a first discrete signal (a signal sampled at a first sampling rate f1). A band pass portion 2 operates at a second sampling rate f2, performs a frequency selecting operation to a second discrete signal (generated when the first discrete signal generated by the low frequency signal generating portion 1 is inputted), and generates a modulated signal with a prescribed center frequency.
Description
The present invention relates to modulator, relate in particular to modulator with the modulated carrier that transmits that will be launched.
At first, be described in a kind of modulator of disclosing among the open No.6-152675 of Japan Patent (below be called " first modulator ") referring to Figure 12, this illustrates its frame structure.In Figure 12, first modulator is that a kind of usefulness transmits modulated carrier to produce the device of modulated signal, and it comprises quadrature base band generator 71, orthopole coordinate converter 72, phase accumulator 73, adder 74, sinusoidal wave table memory 75, multiplier 76 and D/A converter 77.
Quadrature base band generator 71 is transformed to digital orthogonal baseband signal to supplied with digital signal.When the carrier wave that a modulated signal is expressed as two mutually orthogonals synthetic, digital orthogonal baseband signal is represented the amplitude and the phase place of these carrier waves.Orthopole coordinate converter 72 is transformed to a phase-modulated signal and an amplitude-modulated signal to digital orthogonal baseband signal.When expression modulated signal in polar coordinate system, phase-modulated signal and amplitude-modulated signal are represented the phase place and the amplitude of modulated signal.Adder 74 is the output addition of phase-modulated signal and phase accumulator 73.Sinusoidal wave table memory 75 is according to the output of adder 74 and the carrier signal of sine wave output.Multiplier 76 usefulness amplitude-modulated signals are taken advantage of carrier signal.Like this, first modulator produces modulated signal with the phase place and the changes in amplitude of regulation.
Secondly, be described in a kind of modulator of disclosing among the open No.6-244883 of Japan Patent (below be called " second modulator ") referring to Figure 13 and Figure 14 a to 14d, Figure 13 illustrates its frame structure, and Figure 14 a to 14d illustrates the output waveform from each parts.
In Figure 13, modulator comprises signal point arrangement circuit 81, complex coefficient BPF (band pass filter) 82, latch 83, D/A converter 84 and simulation BPF 85, and this modulator does not produce trigonometric function and just realized modulation.
Signal point arrangement circuit 81 output orthogonal baseband signals.Digital orthogonal baseband signal is with sampling rate f
CThe signal of/2 samplings, thereby it has f
CThe harmonic component of/2 integral multiple is shown in Figure 14 a.Complex coefficient BPF 82 is transformed to multiple band (complex band) signal to digital orthogonal baseband signal, to select predetermined band.So, shown in Figure 14 b, in the digital orthogonal baseband signal that is shown in Figure 14 a, only be chosen in the component in the allocated frequency band.Latch circuit 83 and D/A converter 84 usefulness duty ratios are taken advantage of the real signal component of multiple band signal less than 1 pulse, to realize pulse amplitude modulation.Analog band-pass filter 85 extracts desired harmonic component in the output of D/A converter 84.Here because 84 conversion real signal component of D/A converter, so the output signal of D/A converter 84 cause signal shown in Figure 14 b obscure component (aliasing component), it is at f
S(operating frequency of complex coefficient BPF 82) located superimposed.Simulation BPF 85 only extracts the harmonic component of regulation in the output signal of D/A converter 84, to produce the modulated signal shown in Figure 14 d.
As mentioned above, first modulator has the trigonometric function generation part that comprises phase accumulator 73 and sinusoidal wave table memory 75.Trigonometric function produces part is higher than above-mentioned frequency of carrier signal (centre frequency of modulated signal) twice at least with frequency clock work.That is, for first modulator, must produce part (it is a kind of circuit of complexity) with the frequencies operations trigonometric function that is higher than the frequency of modulated wave twice at least, thereby cause the increase of circuit size and power consumption unfriendly.
As second modulator, can construct modulator without part takes place trigonometric function.But in this case, owing to need analog band-pass filter, this is unsuitable for the integrated of circuit.In addition, in second modulator, the centre frequency of modulated signal is limited to f
C/ 2 integral multiple can not easily change it.
Therefore, an object of the present invention is to provide a kind of modulator, it can have less circuit size and lower power consumption, can change the centre frequency of modulation signal simply, and be suitable for integrated.
A first aspect of the present invention is the device that transmits modulated carrier that a kind of usefulness will be launched, and this device comprises:
Discrete signal produces part, is used for the transmit sampling of first sampling rate to importing from the outside, and produces discrete signal; And
The logical part of band, be used for when input when discrete signal produces the discrete signal that part produces, to be higher than the second sampling rate work of first sampling rate, the line frequency band of going forward side by side is selected, and is present in signal in the allocated frequency band with selection.
In first aspect, because band leads to part with the second sampling rate work, therefore input is identical with importing first discrete signal with the signal that the sampling of second sampling rate obtains with the discrete signal of first sampling rate sampling.The logical part of band is carried out frequency band for discrete signal and is selected, and selects the signal that is present in the allocated frequency band as modulated signal (by the signal that obtains with the modulated carrier that transmits that will be launched).
As mentioned above, band is logical partly with the second sampling rate work, and only carries out the frequency band selection operation.Part takes place with the second sampling rate work in the trigonometric function of the modulator that hypothesis is traditional now.The structure that part takes place trigonometric function is very complicated.So the power consumption that part takes place with trigonometric function is compared, the power consumption of the logical part of band is less.In addition, because the discrete signal before the logical part of band part takes place with the first quite low sampling rate work, therefore can make low in energy consumption.
In addition, in first aspect, unlike traditional modulator, can part (its circuit structure is very complicated) take place without trigonometric function and just can produce modulated signal.
Therefore, according to first aspect, can make the circuit size of modulator less lower with power consumption.
According to second aspect, in first aspect, discrete signal generating unit branch comprises low pass filter, is used for when when outside input transmits, with the first sampling rate work and only by being present in the signal in the low frequency.
As mentioned above, a part low pass filter generation discrete signal in order to the first sampling rate work takes place in discrete signal.Therefore, according to second aspect, can make the circuit size of modulator less lower with power consumption.
According to the third aspect, in first aspect, the frequency band that transmits limits in advance, and discrete signal generating unit branch comprises interpolation filter, when when outside input transmits, transmits with the first sampling rate interpolation with this filter.
As mentioned above, part takes place only with interpolation filter (it transmits with the first sampling rate interpolation) generation discrete signal in discrete signal.Therefore, according to the third aspect, can make the circuit size of modulator less lower with power consumption.
According to fourth aspect, in first aspect, the frequency band that transmits limits in advance, and take a sample with first sampling rate, and discrete signal generating unit branch comprises that part and multiplication part take place trigonometric function, the former is used for producing trigonometric function with the frequency of regulation, and the latter is used for when when the outside input transmits, and takes advantage of and transmits so that the trigonometric function of generation to take place at trigonometric function in the part.
According to fourth aspect, part and multiplication part take place because discrete signal generating unit branch comprises trigonometric function, therefore can freely be offset the centre frequency of discrete signal.So, the centre frequency of discrete signal can at random be set.Part takes place trigonometric function and multiplication partly is the structure member that part takes place discrete signal, thereby with the first lower sampling rate work, this makes that also power consumption is lower.
According to the 5th aspect, in first aspect, discrete signal generating unit branch comprises low pass filter and interpolation filter, the former is used for when when outside input transmits, only by being present in a signal in the low frequency, the latter is used for first sampling rate carrying out interpolation by transmitting of low pass filter restricted band.
According to the 5th aspect, because discrete signal generating unit branch comprises low pass filter and interpolation filter, therefore needn't limit the frequency band that transmits, also needn't take a sample with first sampling rate.Therefore, this has improved the availability of modulator.In addition, aspect the 5th, unlike traditional modulator, can part (its circuit structure is very complicated) take place without trigonometric function and produce modulated signal.Therefore,, compare, can make circuit size less lower with power consumption with traditional modulator according to the 5th aspect.
According to the 6th aspect, in first aspect, discrete signal generating unit branch comprises that part and multiplication part take place for low pass filter, trigonometric function, low pass filter is used for when when outside input transmits, with the first sampling rate work and only by being present in a signal in the low frequency, part takes place and is used for producing trigonometric function with the frequency of regulation in trigonometric function, and multiplication partly is used for taking advantage of with the trigonometric function that produces in trigonometric function generation part the output signal of low pass filter.
According to the 6th aspect,, therefore needn't limit the frequency band that transmits because discrete signal generating unit branch comprises low pass filter.So this has improved the availability of modulator.In addition, according to the 6th aspect, because as fourth aspect, discrete signal generating unit branch comprises that part and multiplication part take place trigonometric function, and therefore the centre frequency of modulated signal can at random be set.In addition, these parts make that with lower speed operation the power consumption of modulator is lower.
According to the 7th aspect, in first aspect, the frequency band that restriction in advance transmits, and discrete signal generating unit branch comprises that part and multiplication part take place for interpolation filter, trigonometric function, interpolation filter is used for importing from the outside and carrying out interpolation with transmitting of the first sampling rate restricted band and export the result then, part takes place and is used for producing trigonometric function with the frequency of regulation in trigonometric function, and multiplication partly is used for taking advantage of with the trigonometric function that produces in trigonometric function generation part the output signal of interpolation filter.
According to the 7th aspect, because discrete signal generating unit branch comprises interpolation filter, therefore needn't be with first sampling rate to the sampling that transmits.So this has improved the availability of modulator.In addition, according to the 7th aspect, because as fourth aspect, discrete signal generating unit branch comprises that part and multiplication part take place trigonometric function, and therefore the centre frequency of modulated signal can at random be set.In addition, these parts make that with lower speed operation the power consumption of modulator is lower.
According to eight aspect, in first aspect, discrete signal generating unit branch comprises that part and multiplication part take place for low pass filter, interpolation filter, trigonometric function, low pass filter be used for when when outside input transmits only by being present in the signal of low frequency, interpolation filter is used for first sampling rate output signal of low pass filter being carried out interpolation and exports the result then, part takes place and is used for producing trigonometric function with the frequency of regulation in trigonometric function, and multiplication partly is used for taking advantage of with the trigonometric function that produces in trigonometric function generation part the output signal of interpolation filter.
According to eight aspect, because discrete signal generating unit branch comprises low pass filter and interpolation filter, therefore needn't limit the frequency band that transmits, also needn't take a sample with first sampling rate.Therefore, this has improved the availability of modulator.In addition, according to eight aspect, because as fourth aspect, discrete signal generating unit branch comprises that part and multiplication part take place trigonometric function, and therefore the centre frequency of modulated signal can at random be set.In addition, these parts make that with lower speed operation the power consumption of modulator is lower.
According to the 9th aspect, in first aspect, the logical part of band comprises iir filter, and when input during at the discrete signal that discrete signal takes place to produce in the part, and iir filter is with the second sampling rate work, and carries out the frequency band selection.
According to the 9th aspect because the logical part of band comprises iir filter, therefore be described below the tenth on the one hand the FIR filter relatively, can reduce tap (tap) number of filter, thereby make that the circuit size of modulator is less and power consumption is lower.
According to the tenth aspect, in first aspect, logical leapfrog (leapfrog) iir filter that partly comprises of band, and when importing the discrete signal that produces in discrete signal generation part, the leapfrog iir filter is with the second sampling rate work and carry out the frequency selection.
According to the tenth aspect, because the logical part of band comprises the leapfrog iir filter, therefore compare with the FIR filter in above-mentioned the 9th aspect, can reduce the accuracy of the element that constitutes filter, and make that also the circuit size of modulator is less and power consumption is lower.
According to the tenth one side, in first aspect, the logical FIR filter that partly comprises of band, and when importing the discrete signal that produces in discrete signal generation part, the FIR filter is with the second sampling rate work and carry out the frequency selection.
According to the tenth one side, because the logical part of band comprises the FIR filter, the accuracy that therefore constitutes the element of filter can be the same low with the accuracy that will guarantee in I/O place of being with logical part.So this also can be with higher speed operation FIR filter.
According to the 12,13,14 or 15 aspects, respectively second, the 5th, the 6th or eight aspect, when the logical part of band comprised iir filter or FIR filter, the frequency that low pass filter has can compensate the frequency that iir filter or FIR filter have by characteristic and pass through characteristic.
When the logical part of band comprises iir filter or FIR filter, the amplitude of modulated signal and the situation that phase characteristic is upset are arranged.Therefore, according to the 12 to the 15 aspect, make band pass filter have above-mentioned frequency and pass through characteristic.This has improved the quality of modulated signal.
According to the 16,17,18 or 19 aspects, respectively the the 4th, the 6th, the 7th or eight aspect, the logical part of band is when carrying out the frequency band selection, take advantage of the signal of current input with being stored in wherein coefficient, and before carrying out the frequency band selection operation, multiplier divides according to the trigonometric function that the part generation takes place at trigonometric function determines coefficient, and the coefficient storage of determining in the multiplication part is led to part at band.
As mentioned above, the coefficient of part and the logical part of the partly definite band of multiplication takes place in trigonometric function.According to the 16 to the 19 aspect, needn't add the coefficient that a structure is determined the logical part of band in addition, this makes that the circuit size of modulator is less.
According to the 20 aspect, in first aspect, part and the logical part of band take place and all are made of the parts that are used to carry out Digital Signal Processing in discrete signal.
According to the 20 aspect, because without analog component, so modulator is suitable for integrated.
From can make these and other purpose, feature, aspect and advantage of the present invention become more obvious below in conjunction with the accompanying drawing detailed description of the present invention.
Fig. 1 is the block diagram according to the modulator of first embodiment of the invention;
Fig. 2 a and 2b illustrate from the figure of low frequency signal generation part 1 with the time waveform of first discrete signal of being with logical part 2 to produce and second discrete signal;
Fig. 3 a to 3c be first discrete signal that produces from low frequency signal generation part shown in Figure 11 is shown, from the figure of the frequency spectrum of second discrete signal that produces with logical part and modulating wave;
Fig. 4 a and 4b are the figure that the frequency spectrum of first discrete signal and second discrete signal when the centre frequency of first discrete signal is 0 is shown;
Fig. 5 a and 5b are the figure that the frequency spectrum of first discrete signal and second discrete signal when the centre frequency of first discrete signal is not 0 is shown;
Fig. 6 is the block diagram that the detailed structure of low frequency signal generation part 1 shown in Figure 1 is shown;
Fig. 7 is the block diagram that the detailed structure of a kind of iir filter (it is the structure example that band shown in Figure 1 leads to part 2) is shown;
Fig. 8 is the block diagram that leapfrog iir filter detailed structure is shown, and this filter is the example that band shown in Figure 1 leads to the structure of part 2;
Fig. 9 is the block diagram that the detailed structure of each integrator 17 that is included in the leapfrog filter shown in Figure 8 is shown;
Figure 10 is the block diagram that the detailed structure of FIR filter is shown, and this filter is the example that band shown in Figure 1 leads to part 2 structures;
Figure 11 is the block diagram according to the modulator of second embodiment of the invention;
Figure 12 is the block diagram that is illustrated in a kind of traditional modulator structure that discloses among the open No.6-152675 of Japan Patent;
Figure 13 is the block diagram that is illustrated in a kind of traditional modulator structure that discloses among the open No.6-244833 of Japan Patent; And
Figure 14 a to 14d is the spectrogram that illustrates from the signal that is included in each parts output shown in Figure 13.
What describe in detail below is embodiments of the invention according to accompanying drawing.
(first embodiment)
Fig. 1 is the block diagram that illustrates according to the structure of the modulator of first embodiment of the invention.In Fig. 1, modulator comprises low frequency signal generation part 1 (corresponding to " the discrete signal generating means " in claims) and the logical part 2 of band.
Low frequency signal generation part 1 is with the first sampling rate f
1To from the signal that will be launched of outside input (below be referred to as " transmitting ") sampling, to produce and to export first discrete signal (corresponding to " discrete signal " in claims).
At first discrete signal shown in Fig. 2 a from time waveform, and at the frequency spectrum of first discrete signal shown in Fig. 3 a.In Fig. 2 a, as mentioned above, to the sampling that transmits shown in broken lines among the figure, so first discrete signal comprises in the drawings with the signal series shown in zero mark.In addition, in Fig. 3 a, the frequency spectrum center of first discrete signal is located in assigned frequency (being assumed to be " 0 " now).For make describe clear for the purpose of, in Fig. 3 a, only be illustrated in ± f
1Frequency spectrum in/2 frequency bands.
When taking place partly to import first discrete signal from low frequency signal, the logical part 2 of band is with the second sampling rate f
2(f
2＞f
1) work, select (this will be described later) to carry out frequency band.At this moment, the logical part 2 of band is with f
2Work causes substantially with f
2To the sampling of first discrete signal, and produce second discrete signal.
Fig. 2 b illustrates the time waveform of second discrete signal, and Fig. 3 b illustrates the frequency spectrum of second discrete signal.Shown in Fig. 2 b, when with f
2When first discrete signal is taken a sample, because f
2＞f
1, therefore the point that does not have first discrete signal is arranged.At this some place, occur 0, and constitute signal series (using among the figure ● expression).On the other hand, at the some place that first discrete signal exists, the signal series (representing with zero among the figure) corresponding to the amplitude of first discrete signal appears.Therefore, the waveform of second discrete signal comprises in the drawings with zero He ● the signal series of expression.In addition, in Fig. 3 b, the frequency spectrum of second discrete signal is present in such position, it be by with the frequency spectrum of first discrete signal (referring to a) working frequency f of Fig. 3
1The frequency displacement of integral multiple obtain.For make describe clear for the purpose of, in Fig. 3 b, only illustrate and be present in-f
2/ 2 and+f
2Frequency spectrum in the frequency band between/2.
The selection of the logical part 2 (referring to Fig. 1) of band is present in the interior component of allocated frequency band of the frequency spectrum of second discrete signal, with the output modulated signal.Now, suppose to lead to the frequency band of part 2 selections from 3f by band
1-B to 3f
1+ B, then modulated signal has the frequency spectrum shown in Fig. 3 c.Modulated signal is to be 3f with transmitting to frequency
1Carrier wave modulate and the signal that obtains.
Frequency spectrum, the first sampling rate f of first discrete signal and modulated signal have been described here,
1With the second sampling rate f
2Between relation.
Present hypothesis will be f from the centre frequency of the modulated signal of modulator output
C, and the frequency bandwidth that it occupies is ± B that its center is at f
CAt this moment, according to sampling theory, must be at least 2 (f
C+ B) be chosen as f
2By with f
2Divided by Integer n, f
2/ n is chosen as f
1Yet,, need f for preventing interference from adjacent spectra
1＞2B.
When shown in Fig. 4 a, the frequency spectrum of first discrete signal has when the center that frequency " 0 " is located, by to first discrete signal with f
2The frequency spectrum center of second discrete signal of sampling appears at such position, and shown in Fig. 4 b, they are according to the centre frequency of first discrete signal, get f
1Integral multiple obtain.That is, when hypothesis k is a suitable integer, f
C/ k is chosen as f
1
In addition, shown in Fig. 5 a, when the frequency spectrum of first discrete signal has center at the optional frequency place, by with f
2The center of the frequency spectrum of second discrete signal that sampling obtains to first discrete signal appears at these positions, and shown in Fig. 5 b, they are according to the centre frequency of first discrete signal, get f
1Integral multiple obtain.That is, every f
1The frequency spectrum center of second discrete signal appears in part, allows them with f
1Frequency bandwidth be offset arbitrarily.Therefore, when the frequency spectrum of first discrete signal has center at the optional frequency place, f can be set independently
1And f
C
Next one example of the structure of low frequency signal generation part 1 is described referring to Fig. 6.In Fig. 6, low frequency signal generation part 1 comprises low pass filter 51, interpolation filter 52 and frequency translation part 53.In addition, frequency translation part 53 has multiplication part 55 and trigonometric function generation part 54 (in Fig. 6, frequency translation part 53 is parts that with dashed lines fences up).
Yet, when in advance to the symbol value restricted band, that is, when the restricted signal of frequency band is directly imported low frequency signal generation part 1, just do not need this low pass filter 51.
52 pairs of interpolation filters from the signal of the frequency limited system of low pass filter 51 or outside input with sampling rate f
1Carry out filtering, so that low frequency part passes through, thus with the first sampling rate f
1The restricted signal of frequency band to input carries out interpolation.That is, interpolation filter 52 the sampling rate of the restricted signal of frequency band from f
LBe converted into f
1The output signal of interpolation filter 52 has and the identical frequency spectrum of frequency spectrum shown in Fig. 3 a.Here, general, f
1The speed that obtains divided by integer arbitrarily is as f
LThat is f,
L＜f
1Like this, when to the output signal of interpolation filter 52 with f
2During sampling, (referring to Fig. 2 b) can make the interval that occurs in the frequency spectrum broaden by improving sampling rate.So for for the characteristic of the band pass filter that comprises in the logical part 2 of band of back, moderate characteristic is just enough, allows the size of band pass filter less thus.
When originally with bigger f
LDuring to the restricted sample of signal of frequency band, owing to work as with f
2It is big that interval in the frequency spectrum that occurs during sampling becomes, and just can obtain having the signal of the frequency spectrum shown in Fig. 3 a without the transform sampling rate, so do not need interpolation filter 52.
The trigonometric function generation part 54 that is included in the frequency translation part 53 produces trigonometric function with the frequency of stipulating.As mentioned above, have such situation, wherein, first discrete signal has and is not that 0 centre frequency arbitrarily (referring to Fig. 5 a).The frequency of above-mentioned trigonometric function is determined its centre frequency.
Like this, trigonometric function generation part 54 and multiplication part 55 are with f
1Work, f
1Be lower than final sampling rate f
2On the other hand, for first modulator, need be to be fit to f
2〉=2 (f
C+ B) clock rate comes phase of operation accumulator 73 and sinusoidal wave table memory 75 (they are corresponding to trigonometric function generation part).So, to compare with first modulator, trigonometric function generation part 54 of this modulator and multiplication part 55 can be so that circuit size be less and power consumption is lower.
In addition, having only just needs frequency translation part 53 when first discrete signal that produces shown in Fig. 5 a, and when the generation centre frequency be that " 0 " (does not need frequency translation part 53 during referring to a) first discrete signal of Fig. 3.
In addition, suppose interpolation filter 52 output signals are inputed to multiplication part 55 and described multiplication part 55, but obvious from above, there is such situation, wherein, directly import the output signal that transmits or import low pass filter 51 from the outside.
One example of the structure of the logical part 2 of band is described below.When the frequency spectrum of the modulated signal that is produced by this modulator is symmetrical, shown in Fig. 3 c, as amplitude-modulated signal and BPSK (binary phase shift keying) modulated signal, and the frequency spectrum of first discrete signal is when having the center at frequency 0 place, and first discrete signal becomes real signal.Therefore, has the filter of real coefficient as the logical part 2 of band.
In other situations, that is, asymmetric when the frequency spectrum of modulated signal, perhaps shown in Fig. 5 a, when the frequency spectrum of first discrete signal has when not being the center at 0 optional frequency place, first discrete signal becomes complex signal.Therefore, for the logical part 2 of band, must use filter with complex coefficient.Yet, since the frequency component that will be selected by the logical part 2 of band greater than 0 less than f
2/ 2, therefore just much of that from the real component or the complex number components that need only the output of output complex coefficient filter with logical part 2.
Particularly, by using IIR shown in Figure 7 (infinite impulse response) filter can realize being with logical part 2.In Fig. 7, iir filter comprises multiplier 11
0To 11
N, multiplier 12
0To 12
N, adder 13
0To 13
NWith delay element 14
0To 14
N, multiplier 11
0To 11
NBe used for coefficient b
0To b
NWith each output multiplication, multiplier 12
0To 12
NBe used for coefficient a
0To a
NMultiply each other adder 13 with the value of feedback of each output
0To 13
NBe used for a plurality of input value additions, and delay element 14
0To 14
NBe used for input value is provided delay T.Adder 13
NBy multiplier 11
NWith multiplier 12
NTwo of input take advantage of the value addition, and the value that obtains exported to delay element 14
NAdder 13
(N-1)To 13
1By multiplier 11
(N-1)To 11
1With multiplier 12
(N-1)To 12
1The input two take advantage of value and by delay element 14
NTo 14
2The value addition of input, and a result who obtains exports delay element 14 to
(N-1)To 14
1Adder 13
0From multiplier 11
0The input take advantage of value and from delay element 14
1The value addition of input is so can draw the output of iir filter.In addition, since iir filter with the second sampling rate f
2Carry out aforesaid operations, when input first discrete signal, iir filter only selects to be present in the component (referring to Fig. 3 b and Fig. 5 b) in the allocated frequency band in the frequency spectrum that is included in second discrete signal, to produce modulated signal.
By the way, for iir filter shown in Figure 7, the variation of output valve is to coefficient a
1To a
NAnd b
1To b
NSensitivity, the accuracy that therefore constitutes the operation element of filter must be very high.Yet, when the operation element that is used for filter has high accuracy,, therefore can do the size of filter little because the tap number N of iir filter can be less.
As one type of above-mentioned iir filter, realized a kind of leapfrog filter (having Digital Signal Processing) of announcement in " Design of Analog Filter " (M.E.VanValkenburg work), as shown in Figure 8.Leapfrog filter comprises multiplier 15
0To 15
5, subtracter 16
1To 16
5And integrator 17
1To 17
4
In addition, in leapfrog filter, used the one of four states variable, and integrator 17
1To 17
4Each has a state variable.As shown in Figure 9, integrator 17
1To 17
4Has adder 18 respectively
1To 18
4, delay element 19
1To 19
4And multiplier 20
1To 20
4Adder 18
1To 18
4The output valve of input value and feedback (from multiplier 20
1To 20
4Output) addition.Delay element 19
1To 19
4To adder 18
1To 18
4Output valve provide length of delay T.Multiplier 20
1To 20
4Use coefficient e
1Take advantage of delay element 19
1To 19
4Output valve, export the result then.
Now again referring to Fig. 8.When filter constitutes with analog filter, multiplier 15
0Coefficient r and multiplier 15
5Coefficient y corresponding to output stage resistance and input stage resistance.In addition, multiplier 15
1With 15
3Coefficient k
1And k
3Corresponding to the inductance of analog filter, and multiplier 15
2With 15
4Coefficient k
2And k
4Electric capacity corresponding to analog filter.Filter passes through multiplier 15
0To 15
4Output feed back to subtracter 16
1To 16
4And work.
Iir filter shown in the image pattern 7 is such, leapfrog filter also selects to be present in component in the allocated frequency band with the generation modulated signal as the logical part 2 of band from frequency spectrum, this frequency spectrum is included in second discrete signal that produces by only importing first discrete signal (referring to Fig. 3 b and Fig. 5 b).
By the way, compare with general iir filter, the change of the output valve of leapfrog filter is more insensitive to the coefficient of filter.So, can make the accuracy of operation element of structure leapfrog filter be lower than the accuracy of the operation element in the general iir filter situation.
In addition, can realize being with logical part 2 with FIR (finite impulse response (FIR)) filter, as shown in figure 10.In Figure 10, the FIR filter comprises N tap, comprises multiplier 21
0To 21
N, delay element 23
1To 23
NWith adder 22
0To 22
N, multiplier 21
0To 21
NBe used for coefficient c
0To c
NTake advantage of each to input to the input value of multiplier and export the result, delay element 23
1To 23
NBe used for each input value that inputs to multiplier is postponed T to one, and adder 22
0To 22
NBe used for a plurality of input value phase adduction output results.Obvious from Figure 10, in the FIR filter, multiplier 21
0With coefficient c
0Take advantage of input value, and multiplier 21
1To 21
NWith coefficient c
1To c
NTake advantage of delay element 23
1To 23
NOutput valve.Delay element 23
1(1 is not less than 2) is to delay element 23
(1-1)Output valve postpone T to one.Then, by multiplier 21
0To 21
NBe result that multiplication obtains by adder 22
1To 22
NIn addition comprehensive and become the output of FIR filter.
In addition, the iir filter in the image pattern 7 etc. are such, when input first discrete signal, only select to be present in component (referring to Fig. 3 b and Fig. 5 b) in the allocated frequency band of frequency spectrum of second discrete signal as the FIR filter of the logical part 2 of band to produce modulated signal.
By the way, when the FIR filter being used to be with logical part 2, need very big tap number N.Yet, can be the same low owing to constitute the accuracy of the operation element of FIR filter with the accuracy that will guarantee in I/O place of the logical part 2 of band, therefore can be with higher speed operation modulator.
Figure 10 illustrates the principle of FIR filter, and the number of the multiplier in side circuit can be littler than the number shown in the figure.That is, second discrete signal that produces in the FIR filter has such signal series, and wherein most of signals show 0, shown in Fig. 2 b.So, second discrete signal is being inputed to multiplier 21
0To 21
NBefore, the delay element by each previous stage provides delay to second discrete signal.Therefore, not every multiplier 21 is exported the result who is multiplied each other and obtained by non-zero simultaneously.So, consider the miniaturization of modulator, doing like this is effectively, that is, thereby structure FIR filter comprises the multiplier that number is less, and carries out filtering when switching to multiplier 21 (result that its output is multiplied each other and obtained by non-zero).
In addition, when iir filter during as the logical part 2 of band, amplitude and phase characteristic that frequency can interference output signals.On the other hand, when using the FIR filter, frequency can the interference magnitude characteristic.At this moment, when low frequency signal generation part 1 (referring to Fig. 1) comprises low pass filter 51 (referring to Fig. 6), and the frequency of filter 51 has the characteristic opposite with above-mentioned interference by characteristic, when as whole modulator, can eliminate the interference of amplitude and phase place aspect.
When the logical part 2 of band comprises iir filter or when comprising the FIR filter, the logical part 2 of band just can freely change centre frequency f as long as rewrite each coefficient
CThe value that will be provided with as the coefficient of IIR and FIR filter is described below.Generally,, design an original filter (this original filter has the frequency identical with the FIR filter with IIR by characteristic, and its centre frequency is 0), draw the coefficient of original filter thus in order to realize above-mentioned IIR and FIR filter.Then, the coefficient of original filter be multiply by s shown in following (1) formula
K, the result is got the coefficient of making IIR or FIR filter.
s
K=cos2πkf
C/f
2+j?sin2πkf
C/f
2 ………(1)
Yet, just making the input term signal of multiplication by coefficient, k is a relevant integer, and the number of sample delay when input signal multiply by coefficient is shown.Particularly, for example, when using s
0The time, can obtain b
0(referring to Fig. 7) and c
0(referring to Figure 10), and when using s
1The time, can obtain a
1And b
1(referring to Fig. 7) and c
1(referring to Figure 10).Can draw other coefficient with identical method.f
CBe the centre frequency of modulated signal, f
2Be second sampling rate, and j is empty unit.
Because pass through multiplication part 55 with s
KThe processing of coefficient of taking advantage of original filter is corresponding to the processing of multiplying each other with trigonometric function when the increment of a regulation of phase change, and this is handled with identical by the frequency conversion process of frequency translation part 53 works.So, when low frequency signal generation part 1 comprises frequency translation part 53, can be with the circuit of frequency translation part 53 as the coefficient of IIR that rewrites the logical part 2 of structural belt or FIR filter.As second embodiment, referring to Figure 11 the modulator with this structure is described, the figure shows its frame structure.
(second embodiment)
Compare with modulator shown in Figure 1, the difference of the modulator among Figure 11 is that it also comprises coefficient generation part 61.Because except above-mentioned difference, therefore its general structure partly gives identical label to corresponding structure with shown in Figure 1 identical, and omits description of them.In addition, compare with low frequency signal generation part 1 shown in Figure 6, the difference of the low frequency signal generation part 1 among Figure 11 only is that it also comprises switch 62 and 63, then give other corresponding parts with identical label, and omit description of them.
The coefficient of the original filter that 61 storages of coefficient generation part obtain as mentioned above.The terminal (a) that is included in the switch 62 is connected to interpolation filter 52, the terminal (b) that is included in the switch 62 is connected to coefficient generation part 61, and interpolation filter 52 or coefficient generation part 61 are connected to frequency translation part 53 by switching.In addition, the terminal (a) that is included in the switch 63, be connected to the signal input part of the logical part 2 of band, the terminal (b) that is included in the switch 63 be connected to the logical coefficient input partly of band, and signal input part or coefficient input are connected to frequency translation part 53 by switching.
The operation of modulator is described below.When producing modulated signal, switch 62 and 63 all selects terminal (a) to be connected to interpolation filter 52 and frequency translation part 53.At this moment, can understand the operation of modulator, so omit description to it from first embodiment.
On the other hand, when changing the centre frequency of modulated signal, switch 62 and 63 all selects terminal (b) to be connected to coefficient generation part 61 and frequency translation part 53.Then, the coefficient of the original filter of exporting from coefficient storage part 61 is exported to multiplication part 55.Trigonometric function from trigonometric function generation part 54 is inputed to multiplication part 55, and multiplication part 55 is taken advantage of the coefficient of original filter with trigonometric function, to produce and output is included in the IIR in the logical part 2 of band or the coefficient of FIR filter.The coefficient that produces with said method is exported to the logical part 2 of band, and in the register of storage IIR or FIR filter coefficient etc., be provided with.
Operation when more specifically describing multiplication part 55 calculating IIR or FIR filter coefficient here.When using iir filter shown in Figure 7, multiplication part 55 must design factor a
1To a
NAnd b
1To b
N, when using Fig. 8 and leapfrog filter shown in Figure 9, multiplication part 55 must design factor e
1, and when using FIR filter shown in Figure 10, multiplication part 55 must design factor c
0To c
NNow, all these coefficients are referred to as f
K(k=0,1 ..., N).In addition, the coefficient of original filter is referred to as gK.At this moment, multiplication part 55 is used the s that is shown in following formula (1)
KCalculate f
K=g
KS
K, and export the result to band logical part 2.
As mentioned above, in the modulator according to present embodiment, need not use trigonometric function generation part, perhaps, if use trigonometric function generation part, then its operating rate is lower, allows less circuit size and lower power consumption.In addition, can change the centre frequency of modulated signal as required by the coefficient that changes the filter (IIR or FIR) that constitutes the logical part of band.In addition, though if the structure member of modulator is all constructed with digital element to be convenient to integratedly, they can be constructed with analog element.
Though described the present invention in detail, top description all is illustrative and not restrictive in all respects.Should be appreciated that, can make other change and the change and do not depart from scope of the present invention of many kinds.
Claims (20)
1. one kind with the device that transmits modulated carrier that will be launched, and it is characterized in that comprising:
The discrete signal generating means is used for described the transmit sampling of first sampling rate to importing from the outside, and produces discrete signal; And
Band-pass device is used for operating with second sampling rate that is higher than described first sampling rate when importing at the described discrete signal that described discrete signal generating means produces, and the line frequency band of going forward side by side is selected, to select to be present in the signal in the allocated frequency band.
2. modulator as claimed in claim 1 is characterized in that, described discrete signal generating means comprises low pass filter, be used for when from described the transmitting of outside input, operating with described first sampling rate, and only by being present in the signal in the low frequency.
3. modulator as claimed in claim 1 is characterized in that,
The described frequency that transmits limits in advance, and
Described discrete signal generating means comprises interpolation filter, is used for described first sampling rate described transmitting being carried out interpolation when from described the transmitting of outside input.
4. modulator as claimed in claim 1 is characterized in that,
The described frequency that transmits limits in advance, and with described first sampling rate it is taken a sample, and
Described discrete signal generating means comprises:
The trigonometric function generating means is used for producing trigonometric function with the frequency of regulation; And
Multiplier is used for taking advantage of described transmitting with the trigonometric function that produces in described trigonometric function generating means when from described the transmitting of outside input.
5. modulator as claimed in claim 1 is characterized in that, described discrete signal generating means comprises:
Low pass filter is used for when from described the transmitting of outside input, only by being present in the signal that is lower than in the described frequency that transmits; And
Interpolation filter is used for described first sampling rate being carried out interpolation by described the transmitting of described low-frequency filter restricted band.
6. modulator as claimed in claim 1 is characterized in that, described discrete signal generating means comprises:
Low pass filter is used for when from described the transmitting of outside input, with described first sampling rate operation, and only by being present in the signal that is lower than in the described frequency that transmits;
The trigonometric function generating means is used for producing trigonometric function with the frequency of regulation; And
Multiplier is used for taking advantage of with the trigonometric function that produces at described trigonometric function generating means the output signal of described low pass filter.
7. modulator as claimed in claim 1 is characterized in that,
Described transmitting is frequency band limits in advance, and
Described discrete signal generating means comprises:
Interpolation filter is used for described first sampling rate carrying out interpolation from outside input and restricted described the transmitting of frequency band, and the output result;
The trigonometric function generating means is used for producing trigonometric function and exporting just result with the frequency of regulation; And
Multiplier is used for taking advantage of with the trigonometric function that produces at described trigonometric function generating means the output signal of described interpolation filter.
8. modulator as claimed in claim 1 is characterized in that, described discrete signal generating means comprises:
Low pass filter, be used for when from outside input described transmit only by being present in the signal of low frequency, export this signal then;
Interpolation filter is used for described first sampling rate output signal of described low pass filter being carried out interpolation, exports the result then;
The trigonometric function generating means is used for producing trigonometric function with the frequency of regulation; And
Multiplier is used for taking advantage of with the trigonometric function that produces at described trigonometric function generating means the output signal of described interpolation filter.
9. modulator as claimed in claim 1 is characterized in that,
Described band-pass device comprises iir filter; And
When importing the discrete signal that produces in the discrete signal generating means, described iir filter is operated with described second sampling rate, and carries out described frequency band and select.
10. modulator as claimed in claim 1 is characterized in that,
Described band-pass device comprises the leapfrog iir filter; And
When importing the discrete signal that produces in the discrete signal generating means, described leapfrog iir filter is operated with described second sampling rate, and carries out described frequency band and select.
11. modulator as claimed in claim 1 is characterized in that,
Described band-pass device comprises the FIR filter; And
When importing the discrete signal that produces in the discrete signal generating means, described FIR filter is operated with described second sampling rate, and carries out described frequency band and select.
12. modulator as claimed in claim 2, it is characterized in that, when described band-pass device comprised iir filter or FIR filter, described low pass filter had such frequency by characteristic, and it can compensate the frequency that described iir filter or described FIR filter had and pass through characteristic.
13. modulator as claimed in claim 5, it is characterized in that, when described band-pass device comprised iir filter or FIR filter, described low pass filter had such frequency by characteristic, and it can compensate the frequency that described iir filter or described FIR filter had and pass through characteristic.
14. modulator as claimed in claim 6, it is characterized in that, when described band-pass device comprised iir filter or FIR filter, described low pass filter had such frequency by characteristic, and it can compensate the frequency that described iir filter or described FIR filter had and pass through characteristic.
15. modulator as claimed in claim 8, it is characterized in that, when described band-pass device comprised iir filter or FIR filter, described low pass filter had such frequency by characteristic, and it can compensate the frequency that described iir filter or described FIR filter had and pass through characteristic.
16. tuner as claimed in claim 4 is characterized in that,
Described band-pass device uses the coefficient that is stored in wherein to take advantage of the signal of current input in the moment of carrying out described frequency band selection; And
Before carrying out described frequency band selection operation, described multiplier is determined described coefficient according to the trigonometric function that produces in described trigonometric function generating means, and a coefficient storage of determining in described multiplier is in described band-pass device.
17. tuner as claimed in claim 6 is characterized in that,
Described band-pass device uses the coefficient that is stored in wherein to take advantage of the signal of current input in the moment of carrying out described frequency band selection; And
Before carrying out described frequency band selection operation, described multiplier is determined described coefficient according to the trigonometric function that produces in described trigonometric function generating means, and a coefficient storage of determining in described multiplier is in described band-pass device.
18. tuner as claimed in claim 7 is characterized in that,
Described band-pass device uses the coefficient that is stored in wherein to take advantage of the signal of current input in the moment of carrying out described frequency band selection; And
Before carrying out described frequency band selection operation, described multiplier is determined described coefficient according to the trigonometric function that produces in described trigonometric function generating means, and a coefficient storage of determining in described multiplier is in described band-pass device.
19. tuner as claimed in claim 8 is characterized in that,
Described band-pass device uses the coefficient that is stored in wherein to take advantage of the signal of current input in the moment of carrying out described frequency band selection; And
Before carrying out described frequency band selection operation, described multiplier is determined described coefficient according to the trigonometric function that produces in described trigonometric function generating means, and a coefficient storage of determining in described multiplier is in described band-pass device.
20. modulator as claimed in claim 1 is characterized in that, described discrete signal generating means and described band-pass device all use the element of realizing Digital Signal Processing to construct.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP198919/97 | 1997-07-24 | ||
| JP9198919A JPH1141305A (en) | 1997-07-24 | 1997-07-24 | Modulating device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN1207621A true CN1207621A (en) | 1999-02-10 |
Family
ID=16399150
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN98116396A Pending CN1207621A (en) | 1997-07-24 | 1998-07-24 | Modulator |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US6184756B1 (en) |
| EP (1) | EP0893900A3 (en) |
| JP (1) | JPH1141305A (en) |
| CN (1) | CN1207621A (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100743534B1 (en) * | 2000-01-07 | 2007-07-27 | 코닌클리케 필립스 일렉트로닉스 엔.브이. | Transmission device and method for transmitting a digital information |
| GB2359950B (en) * | 2000-02-29 | 2004-06-30 | Ericsson Telefon Ab L M | Signal filtering |
| JP5274014B2 (en) * | 2004-10-13 | 2013-08-28 | メディアテック インコーポレーテッド | Communication system filter |
| US7342525B2 (en) * | 2005-12-23 | 2008-03-11 | Cirrus Logic, Inc. | Sample rate conversion combined with DSM |
| US7242326B1 (en) * | 2005-12-23 | 2007-07-10 | Cirrus Logic, Inc. | Sample rate conversion combined with filter |
| EP3157112A1 (en) * | 2015-10-12 | 2017-04-19 | General Electric Technology GmbH | Improvements in or relating to the protection of power transformers |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL168099C (en) * | 1974-09-12 | 1982-02-16 | Philips Nv | MODULATION AND FILTER DEVICE FOR DIGITAL SIGNALS. |
| DE4041632A1 (en) * | 1990-03-15 | 1992-07-02 | Ant Nachrichtentech | Preparing several TV signals for transmission - involves frequency conversion and multiplexing with additional digital filter preceding channel bandpass filter with same clock rate |
| US5420887A (en) | 1992-03-26 | 1995-05-30 | Pacific Communication Sciences | Programmable digital modulator and methods of modulating digital data |
| FR2689350B1 (en) * | 1992-03-30 | 1995-04-21 | France Telecom | Amplitude modulator with residual sideband for sampled or digital analog signals and its use in television. |
| JPH06152675A (en) | 1992-11-05 | 1994-05-31 | N T T Idou Tsuushinmou Kk | Digital modulator |
| JP3400003B2 (en) | 1993-02-18 | 2003-04-28 | 株式会社日立製作所 | Complex modulation and demodulation method |
| DE4337134A1 (en) * | 1993-10-30 | 1995-05-04 | Ant Nachrichtentech | Method for processing a digital frequency division multiplex signal |
| US5519732A (en) * | 1994-05-02 | 1996-05-21 | Harris Corporation | Digital baseband to IF conversion in cellular base stations |
| US5783974A (en) * | 1997-01-27 | 1998-07-21 | Hitachi America, Ltd. | Digital interpolation up sampling circuit and digital modulator using same |
-
1997
- 1997-07-24 JP JP9198919A patent/JPH1141305A/en active Pending
-
1998
- 1998-07-21 US US09/119,644 patent/US6184756B1/en not_active Expired - Lifetime
- 1998-07-23 EP EP98113817A patent/EP0893900A3/en not_active Withdrawn
- 1998-07-24 CN CN98116396A patent/CN1207621A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPH1141305A (en) | 1999-02-12 |
| EP0893900A2 (en) | 1999-01-27 |
| EP0893900A3 (en) | 2002-02-06 |
| US6184756B1 (en) | 2001-02-06 |
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